1. Field of the Invention
The present invention relates to a barrier opening and closing apparatus used in an optical system of an optical instrument such as a camera.
2. Related Background Art
Conventionally known as a barrier opening and closing apparatus used in an optical system of an optical instrument such as a camera is one comprising a lever disposed on the outer periphery side of a lens barrel so as to extend in the optical axis direction as disclosed in Japanese Patent Application Laid-Open No. HEI 5-80391 or No. HEI 10-186453. In such a barrier opening and closing apparatus, the lever is rotatably attached to the outer peripheral surface of the lens barrel, whereas a front end portion of the lever is engaged with a ring member, whereby the lever is rotated as the lens barrel rotates, so as to open the barrier by way of the ring member.
Also known is one comprising a driving ring for opening and closing a barrier, and a driving arm extending in the optical axis direction from the driving ring, in which a rotational force is applied to the driving arm by use of a cam mechanism, so as to open and close the barrier by way of the driving ring as disclosed in Japanese Utility Model Publication No. HEI 7-55546.
However, the former barrier opening and closing apparatus disclosed in Japanese Patent Application Laid-Open No. HEI 5-80391 or No. HEI 10-186453 necessitates a lever in addition to a ring member as a component of the apparatus, and it is necessary for the lever to be rotatably attached to the lens barrel in a process of making the apparatus. Therefore, if the barrier is to be opened and closed by use of a lever, then the cost of the lever as a component and the cost of attaching the lever upon manufacture will be necessary.
In the latter barrier opening and closing apparatus disclosed in Japanese Utility Model Publication No. HEI 7-55546, on the other hand, there is a fear of the driving ring failing to rotate smoothly, since there is only one driving arm for applying the rotational force to the driving ring. If the driving arm is formed longer, for example, then not only a force for rotating the ring but also a force for tilting it may apply thereto, so that there is a fear of the driving ring being prevented from rotating smoothly due to a frictional force between the driving ring and a member for holding the driving ring, whereby the barrier may not be opened and closed smoothly.
In order to overcome such problems, it is an object of the present invention to provide a barrier opening and closing apparatus which can lower the cost of apparatus and can smoothly open and close the barrier.
For achieving such an object, the present invention provides a barrier opening and closing apparatus for opening and closing a barrier according to an action of a lens barrel containing an optical lens system; the apparatus comprising a ring member disposed rotatable about an optical axis of the optical lens system and adapted to open and close the barrier according to a rotation thereof, the ring member forming a plurality of rotational force transmitting parts extending rearward therefrom in parallel to the optical axis, a rotational force for opening and closing the barrier being supplied according to the action of lens barrel by way of the rotational force transmitting parts.
The barrier opening and closing apparatus in accordance with the present invention may be configured such that the rotational force transmitting parts of the ring member are engaged with the lens barrel, and the rotational force is transmitted to the ring member by way of the rotational force transmitting parts as the lens barrel rotates.
In the barrier opening and closing apparatus in accordance with the present invention, the rotational force transmitting parts may be formed at substantially equal intervals peripherally of the ring member.
In the barrier opening and closing apparatus in accordance with the present invention, the rotational force transmitting parts may be engaged with the lens barrel at a rear end position thereof.
According to the present invention, a rotational force is directly transmitted to the ring member by way of the rotational force transmitting parts as the lens barrel rotates or moves. Since the rotational force of ring member is transmitted by a plurality of rotational force transmitting members, the ring member smoothly rotates without tilting as the rotational force is transmitted thereto. As a consequence, the barrier can be opened and closed smoothly.
The present invention will become more fully under stood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.